Key lever return mechanism



June 11, 1968 A. A. HAGSTROM 3,387,694

KEY LEVER RETURN MECHANISM Filed Dec. '21, 1966 INVENTOR ARTHUR A. HAGSTROM BY ATTOR Y United States Patent Oflice 3,387,694 Patented June 11, 1968 3,387,694 KEY LEVER RETURN MECHANISM Arthur A. Hagstrom, Roselle, 11]., assignor to Teletype Corporation, Skokie, Ill., a corporation of Delaware Filed Dec. 21, 1966, Ser. No. 603,638 4 Claims. (Cl. 197-98) ABSTRACT OF THE DISCLOSURE A key lever return mechanism including a bar extending the width of a keyboard, a pair of pivots positioned at opposite ends of the bar and a pair of springs attached to opposite ends of the bar for yieldably urging the bar into engagement with the pivots.

BACKGROUND OF THE INVENTION Typewriters and teletypewriters are often provided with a repeat feature whereby a key may be depressed to a first position to type a single character and may be depressed further to a second position to type the character repeatedly. Movement of the key past the first position to the second position is usually opposed by an auxiliary key lever return spring so that the operator of the device can easily distinguish between the two positions. It has been found, however, that if a uniform auxiliary return force is applied to all of the keys of a keyboard the peripheral keys are too difficult to move to the second position by the weaker fingers of an operator and the center keys are too easily moved to the second position by the stronger fingers of an operator.

Accordingly, an object of this invention is to provide a key lever return mechanism which applies a relatively weak return force to the peripheral keys of a keyboard and which applies a relatively strong return force to the center keys of the keyboard.

SUMMARY OF THE INVENTION At least one spring for applying a return force to all of the keys of a keyboard and means for making the amount of force applied to individual keys proportional to the distance between the individual key and the sides of the keyboard.

DESCRIPTION OF THE DRAWING A more complete understanding of the invention may be had by referring to the drawing which is a front view of certain components of a keyboard employing the invention.

DETAILED DESCRIPTION Referring now to the drawing there is shown a keyboard including a frame 11 comprised of a horizontal plate 12 and a vertical plate 13. A plurality of keys 15 are supported in guide holes 16 for-med in the vertical plate 13 for vertical movement with respect to the frame 11. The keys 15 are comprised of key levers 17, keytops 18 mounted on the key levers 17, operating members 19 which extend horizontally from the key levers 17 and which are shown in section in the drawing, and legs 20 which extend downwardly from the key lever 17 through the horizontal plate 12. Each of the keys 15 is urged upwardly by a key return spring 21 individual to it. The key return springs 21 are positioned around the legs 20 between shoulders 24 on the key levers 17 and the horizontal plate 12.

A pair of pivot members 22 and 23 are mounted on the frame 11 at the left and right sides of the keyboard 10, respectively. A key lever return bar 25 is urged into engagement with the pivot members 22 and 23 by a pair of springs 26 and 27 connected between the frame 11 and left and right ends, respectively, of the bar 25. The bar 25 extends transversely with respect to the operating members 19 across the entire width of the keyboard 10.

In use the operating members 19 control a printing mechanism (not shown) so that depression of a key 15 causes a character corresponding to the depressed key to be printed by the printing mechanism. The keyboard illustrated is intended for use in conjunction with printing mechanisms in which characters may be selectively typed a single time or may be typed repeatedly under the control of the keys 15. Accordingly, if a key 15 is depressed to a first position wherein the bottom edge of the operating member 19 of the key is in engagement with the upper edge of the bar 25, the character corresponding to the depressed key is typed a single time. If, however, the key 15 is depressed past the first position to a second position, the character is typed repeatedly.

Since the bar 25 is in the path of travel of the keys 15 from the first position to the second position, movement of the keys past the first position is resisted by the springs 26 and 27 which urge the bar 25 upwardly. The resistance applied to any particular key is dependent upon the position of the key with respect to the sides of the keyboard. For example, if a key at the left-hand end of the keyboard is depressed the bar 25 is pivoted about the pivot 23 against the action of the spring 26. The lever arm through which the force of the spring 26- is applied to the depressed key extends virtually the entire length of the bar 25 and. accordingly, the return force on the depressed key is relatively weak. However, if a center key is depressed either the force of one of the springs 26 or 27 acts on the key through a much shorter lever arm or both of the springs 26 and 27 resist movement of the key. In either case a much stronger return force is applied to a center key than is applied to a peripheral key.

It should be understood that the return force applied to a depressed key is proportional to the distance of the depressed key from the sides of the keyboard. Since the strength of the fingers of an operators hands increases progressively from the little finger to the index finger, the construction illustrated results in a keyboard in which the return force applied to peripheral keys is weak enough to allow movement of the peripheral keys from the first position to the second position by an operators weaker fingers and in which the return force applied to the center keys is strong enough to prevent inadvertent movement of the center keys to the second position by an operators stronger fingers.

Although only one embodiment of the invention is shown in the drawing and described in the foregoing specification, it will be understood that invention is not limited to the specific embodiment described, but is capable of modification and rearrangement and substitution of parts and elements without departing from the spirit of the invention.

I claim:

1. A keyboard including:

a frame;

a plurality of keys mounted on the frame for movement with respect to the frame from a first position to a second position;

a pair of pivots mounted on the frame and positioned on opposite sides of the plurality of keys;

a bar extending between the pivots and positioned adjacent the keys in their paths of travel from the first position to the second position, and

spring means mounted between the bar and the frame for urging the bar toward the pivots and the keys so that whenever one of the keys is moved from the first position to the second position the bar is pivoted about one of the pivots away from the other of the pivots against the action of the spring means.

3 4 2. The keyboard according to claim 1 wherein the spring movement of one of the keys from the first to the means is comprised of a pair of springs, one connected second position in the second direction. between each end of the bar and the frame.

3. The keyboard according to claim 1 further including References Cited two pairs of spaced fingers extending from the bar and positioned on alternate sides of each of the pivots, re-

Cit

spectively for guiding the bar as it is moved away from 1 fi gs 521322 the Plvots by the keys- 2,723,740 11/1955 Toeppen 197-17 4. The keyboard according to claim 1 Wherem: 2 861 262 11/1958 Pankov6 XR the keys extend in a first direction with respect to the 10 z975l97l 3/1961 Schenk 14 frame; 3,229,798 1/1966 Grashoff 197-17 the movement of the keys from the first position to the second position is in a second direction perpendicular OTHER REFERENCES to the first direction; IBM Technical Disclosure Bulletin, Article by H. J. the pivots extend from the frame in the second direc- 15 Ruhnke entitled Keyboard Unit, V01. 3, 4, p

tion, and her 1965, p. 630.

the bar extends under the keys in a third direction perpendicular to both the first and the second directions ROBERT PULFREY Pn'mwy Examine" and pivots about one of the pivots in response to E. S. BURR, Examiner. 

